Harris must now prepare his side for the challenge of Ireland
Iestyn Harris gained his first win as Wales coach with a crushing victory in this European Cup match in Smederevo.
Wales ran in 15 tries at the Fortress Stadium against a single four-pointer from a Serbia side who never gave up.
Wales next face Ireland at Sardis Road, Pontypridd on Sunday, where they will bid to win a European Cup final place.
Wales lost 48-12 to England in a friendly at the Brewery Field, Bridgend, last Saturday, Harris' first game in charge of the side.
The Serbia score was just short of Wales' highest ever, a 92-4 win over USA in a friendly in Philadelphia in 1995.
But it was a record for them in competitive rugby league, surpassing the 74-4 win over Russia at Aberavon in 2003.
Ian Webster kicked 14 conversions and also scored a try to break Jonathan Davies' record of eight goals and 28 points set against Papua New Guinea at Swansea in 1991.
Bridgend Blue Bulls centre Christiaan Roets, who was only allowed into Serbia after the British Embassy intervened to help resolve a visa issue, marked his Welsh debut with a hat-trick of tries and the man-of-the-match award.
Wales' other tries were scored by Elliott Kear, Jordan James (2), Matt Thomas, Ross Divorty (2), Rhys Williams (2), Lee Williams, Ashley Bateman and Ian Watson.
Oldham loose forward Austen Novakovic scored Serbia's solitary try after 10 minutes and stand-off Filip Brkic kicked two goals.